This invention relates to an outboard engine assembly employing a V-type multi-cylinder engine wherein two rows of cam chambers are arranged to serve respectively as a breather chamber and an oil separating chamber by connecting them respectively to an intake upstream side and an intake downstream side, thus effectively utilizing internal volumes of the cam chambers.
An outboard engine assembly which ventilates a crank chamber by introducing fresh air is known from, for example, Japanese Patent Provisional Publication No. HEI-5-214921.
The outboard engine assembly has a structure wherein crank-chamber ventilation control valves (positive crankcase ventilations) (herein after referred to as PCV valves) each composed of a check valve are connected to a crankcase chamber, with the PCV valves of two systems connected to a breather chamber of a cylinder head side connected to upstream and downstream sides of a throttle valve.
Further, Japanese Patent Laid-Open Publication No. HEI-6-117270 discloses an outboard engine assembly employing an engine having a breather chamber.
In the outboard engine assembly disclosed in HEI-5-214921, the breather chamber has a volume in a range determined by a cylinder bore, i.e. staying in a size of the cylinder head cover of one cylinder-row.
It is therefore an object of the present invention to provide an outboard engine assembly having a V-type multi-cylinder engine, which permits internal volumes of respective compartments of an oil separating chamber to be utilized as a breather chamber and enable a fuel pump and the oil separating chamber located at a PCV valve side to be conveniently positioned.
According to an aspect of the present invention, there is provided a outboard engine assembly having a V-type multi-cylinder engine with two cylinder head covers, which comprises a crank chamber, a breather chamber formed in a cam chamber of one row of a V-bank, and an oil separating chamber formed in a cam chamber of the other row of the V-bank, wherein the breather chamber communicates with the crank chamber and is connected to an intake upstream side of a throttle valve unit, wherein a cam chamber forming the oil separating chamber communicates with the crank chamber and is connected to a downstream side of the throttle valve unit via passage, and wherein the passage has a crank-chamber ventilation control valve which opens to an intake downstream side.
The presence of the cam chambers, formed in the cylinder head covers in two rows, which are assigned as the breather chamber and the oil separating chamber having a PCV connected to the intake downstream side enables the breather chamber and the oil separating chamber to have respective required volumes. Especially, the presence of the oil separating chamber having the PCV specifically prepared in the cam chamber independently of the cam chamber serving as the bleed chamber allows the oil separating chamber to be formed with labyrinths for separating oil contaminants, thereby ensuring a volume sufficient for reliably separating the oil contaminants while enabling the volumes of respective cam chambers to be effectively utilized.
The provision of the fuel pump, driven with the camshaft, mounted to the one cylinder head cover allows the fuel pump and the oil separating chamber at the PCV side to be rationally positioned. In particular, the oil separating chamber on the side of the fuel pump is connected to the downstream side of the throttle valve unit via the PCV valve, while allowing the breather chamber, which as a larger volume, to be connected to-the upstream side of the throttle valve unit. As a result, the oil contaminants can be sufficiently removed from the blow-by gas, with a resultant decrease the amount of oil contaminants adhered to the throttle valve unit.